A standard sheet-metal trimming shear of the rotary type is described in German patent document No. 2,138,476 filed July 31, 1971 by W. Reinhardt. It has two pairs of circular cutting blades that are superposed to define a cutting plane parallel to the direction of displacement of the sheet-metal workpiece through the shear and that each constitute a cutting unit. The units are each responsible for a longitudinal edge of the workpiece and are spaced apart across the workpiece transverse to the workpiece travel direction. Transverse spindles can displace the cutting units transverse to the transport direction so the workpiece can be trimmed to the desired size.
These machines are very complicated and quite bulky, particularly those intended for use with thin stock. The initial cost of such an apparatus is very large, and servicing it can be extremely costly. The large size of the devices is also a hindrance in many production lines where the room available, particularly the transverse spacing, between lines is minimal.